GB2267732A

GB2267732A - I.c. engine fuel injection pump control.

Info

Publication number: GB2267732A
Application number: GB9311083A
Authority: GB
Inventors: Karsten Hummel; Karl Rapp; Ernst Ritter
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1992-05-30
Filing date: 1993-05-28
Publication date: 1993-12-15
Also published as: GB9311083D0; JPH0650179A; DE4217940A1; US5291867A

Abstract

A control rod movement limiting device 7 mounted on the pump housing 1 has a piston 9 with a radial pin 13 which extends into a slot 17 of the control rod 5 to limit its movement. The position of the adjusting piston 9 abutting stop 41 determines the maximum cold starting control rod travel and a temperature-dependent memory spring 49 above a predetermined engine temperature moves the piston to bring the ring 53 into abutment with the sleeve 55 and reduce the maximum control rod travel. A pressure chamber 31 may be supplied with compressed air so that the piston 9, through the pin 13, moves the rod 5 to its zero delivery position. <IMAGE>

Description

2267732

DESCRIPTION FUEL INJECTION PUMPS FOR INTERNAL COMBUSTION ENGINES

The invention relates to fuel injection pumps for internal combustion engines.

In a fuel injection pump, known from DE 26 46 546 C2. there is mounted on the pump housing an adjusting device in which an adjusting piston is longitudinally displaceably adjustable parallel to the axis of the control rod of the fuel injection pump by a pressure medium against the force of a return spring. The adjusting device has a radially projecting intermediate member which engages a slotted hole in the control rod via an aperture in the pump housing. The axial boundary edges of the slotted hole in the direction of movement of-the control rod each form, in cooperation with the intermediate member, a respective stop in the direction of the full-load delivery quantity and in the direction of zero delivery quantity which corresponds to a stop position, this stop becoming effective only when the adjusting piston has been displaced. The movement of the adjusting piston initiated by the pressure medium serves to adjust the adjusting piston in the direction of fullload delivery quantity, in that the intermediate member comes into abutment against the boundary edge of the control rod and, during the further course of -2the adjusting movement, the adjusting piston displaces the control rod into a stop position against the force of a drag member on the governor. In this manner, the known adjusting device is used chiefly to stop the internal combustion engine, wherein the position of the maximum delivery quantity is also adjustable by way of a pin forming a stop for the adjusting piston during pressure relief, particularly during starting of the internal combustion engine, by way of the adjusting device. Instead of this, it is possible to make this stop adjustable and to control this adjustment in dependence upon operating parameters of the internal combustion engine, such as the temperature. However, if an adjustable starting quantity and, independently thereof. temperaturedependent control of the starting quantity are to be realised in addition to the stopping function, additional components are required which have to be mounted on the housing of the adjusting device and thus take up additional installation space.

In accordance with the present invention there is provided a fuel injection pump for internal combustion engines, having a housing, pump pistons disposed in line and guided in cylinder liners, each of which pistons defines a respective pump working chambert a control rod mounted in the longitudinal direction of -3the pump in the pump housing and which is longitudinally displaceable by an adjusting member for the purpose of adjusting the quantity of fuel injected by the pump pistons and which is connected to the adjusting member by way of a resiliently yielding drag member, and an adjusting device having an adjusting piston which is adjustable away from a stop by a pressure medium against the force of a return spring and which acts upon the control rod by way of an intermediate member between two further stops, which are located one behind the other in the direction of movement and are disposed on at least one part which is moved together with the control rod during the movement of the latter for adjusting the quantity of fuel injected, for limiting a travel of the control rod predetermined by the distance between the stops. wherein the adjusting piston of the adjusting device is displaceable in dependence upon the operating temperature of the internal combustion engine by a temperature- dependent spring element which is disposed on the periphery of the adjusting piston and which is supported against an abutment fixed relative to the housing and acts against the return spring. in such a way that the possible adjusting travel of the control rod in the direction of a full-load delivery quantity is variably by abutment of one of the further stops against the intermediate member.

This has the advantage that, by disposing the temperature-dependent adjusting member within the adjusting device. the installation space of the adjusting device can be kept small and, in addition to retaining the function of stopping the engine, it is possible to control the starting quantity. For this purpose the adjusting piston is advantageously acted upon by a temperature-dependent spring element which is supported against a stop fixed relative to the housing and expands when heated and acts upon the adjusting piston by way of a stop.

Preferably, this spring element is a Ilmemoryll spring, so that reliable and inexpensive adjustment of the starting quantity is possible.

Preferably, it is possible to vary the adjusting travel of the starting quantity control member, formed by the temperature-dependent spring. from the outside, so that subsequent adjustment of a temperaturedependent fullload stop is still possible.

Preferably, in order also to provide the possibility of adjusting the starting quantity of fuel when starting the cold internal combustion enginef, during which the temperature-dependent starting quantity control member does not become effectiver a further externally operable setscrew is screwed into -5the housing of the adjusting device in such a way that it acts upon the end face remote from the temperaturedependent spring. Thus, by virtue of the construction, in accordance with the invention, of the adjusting device in which all the components serving for the adjustment are located within the housing, it is possible to realise the stopping function by way of a pressure medium. the temperature-dependent starting quantity control and an adjustable starting quantity stop, without enlarging the installation space of a known adjusting device.

By way of example only, a specific embodiment of the invention will now be described, with reference to the accompanying drawings, in which:- Fig. 1 is a partial schematic side elevation of a fuel injection pump, showing the position in which the adjusting device is mounted on the pump housing; and Fig.2 is a cross sectional view through the adjusting device constructed in accordance with the present invention, turned through 900C, with a part of the pump housing contiguous thereto, and the control rod.

A plurality of cylinder liners 3 is inserted in line in a pump housing 1 in the fuel injection pump whose region only material to the invention is shown in Fig. 1. Each of the cylinder liners has a -6cylindrical bore (not illustrated) in which a pump piston (also not illustrated) defining a pump working chamber is axially movable by a cam device and is rotated in a known manner for timing the injection operation, or for regulating the delivery quantity of fuel, by way of a control rod 5 which is moved by a rotational-speed-dependent governor by way of a resilient drag member. This relates to, for example, in-line injection pumps having the known oblique control edge which is provided on the pump piston and which cooperates with a spill port, fixed relative to the housing, in the wall of the cylindrical bore or, alternatively. to injection pumps in which a slider is adjustable on the pump piston by a control rod for the purpose of controlling the quantity of fuel injected and/or the duration of injection, possibly with the pump piston at the same time displaceable by a control rod.

The pump working chamber is in turn connected by way of an injection line (not illustrated) to an injection valve opening into a combustion chamber of the internal combustion engine to be supplied, and is supplied with fuel from a low-pressure chamber surrounding the cylinder liner 3 by way of control ports in the wall of the cylindrical bore. An adjusting device 7 in which, as is shown in Fig. 2, an -7adjusting piston 9 is mounted so as to be displaceable parallel to the axis of the control rod 5, is disposed on the pump housing 1 parallel to the axis of the control rod 5. One end of the adjusting piston 9 has radial bore 11 into which a pin 13 is screwed. The pin 13 extends through a slotted-hole-like window 15 in the wall of the adjusting device 7 and of the pump housing 1 into a slotted hole 17 in, and lying in the longitudinal direction of, the control rod 5. and thus connects the control rod 5 to the adjusting device 7. The axial boundaries of the slotted hole 17 at the same time form two stops for the pin 13,, the left- hand boundary forming a first stop 19 which limits the control travel of the control rod 5 in the direction of the full-load delivery quantity, and the right-hand boundary forming a second stop 12 which limits the control travel of the control rod 5 in the direction of a the zero delivery quantity.

The adjusting piston 9 is slidingly displaceably guided by way of its circumferential surface in a bush 23 formed by a reduction in the cross section within the adjusting device 7. The bush 23 divides the interior of the adjusting device 7 into two regions whose diameters are enlarged relative to the bush 23. In a first of these regions, which is located at the end remote from the pin 13, a flange 27 is disposed at -8the end of the adjusting piston 9 and axially guides a sealing ring 25 at the end of the adjusting piston 9. The outer circumferential surface of the sealing ring 25 slides on the inside wall of the adjusting device 7 and thus separates a chamber 31, defined by the end face 29 of the adjusting piston 9 remote from the pin 13, from the chamber contiguous to the bush 23. The chamber 31, defined by the end face 29 and by a cover 43 axially sealing the adjusting device 7, forms a pressure working chamber 31 which is connectible by way of a pressure medium passage 33 to a source of pressure medium which preferably supplies compressed air. A return spring 35 in the form of a spiral compression spring is disposed on the adjusting piston 9 in the chamber between the bush 23 and the sealing ring 25, and is supported at one end on a shoulder 37, fixed relative to the housing, on the bush 23, and at the other end on an axially secured ring 39, which may be in the form of a circlip, on the adjusting piston 9. When a low pressure prevails in the pressure working chamber 31, the return spring 35 holds the end face 29 of the adjusting piston 9 against an adjustable stop 41 formed by a setscrew 45 which is screwed into the cover 43 axially in line with the adjusting piston 9 and which is secured against independent turning by a nut 47.

A temperature-dependent spring element 49 in the form of a spiral compression spring is disposed on the adjusting piston 9 in that region of the adjusting device 7 which accommodates the pin 13, and is supported at one end against a housing shoulder 51 formed by the bush 23 and at the other end against a guide ring 53 whose side remote from the spring element 49 abuts against the pin 13 and which is axially secured on the adjusting piston 9. The maximum spring travel by which the temperaturedependent spring element 49 expands under heat, and thus the temperature-dependent adjusting travel of the adjusting piston 9, are limited by a slotted sleeve 55, axially guided in the adjusting device 7, in that the guide ring 53 is brought into abutment against one end face of the sleeve 55 by the spring element 49. The slot 57 in the sleeve 55 is constructed in such a way that the radial pin 13 disposed at one end of the adjusting piston 9 is not obstructed by the sleeve 55 during an axial adjusting movement of the adjusting piston 9. The end face 59 of the sleeve 55 remote from the pin 13 is closed and abuts against a further cover 61 which seals that region of the adjusting device 7 which accommodates the temperaturedependent spring element 49. The cover 61, is a disc held axially against an abutment 65 in a housing bore 67 by -10a retaining ring 63F and has a concentric bore into which a setscrew 69 is screwed in such a way that it acts upon the end face 59 of the sleeve 55 when it emerges from the cover 61. It is thereby possible to adjust the temperature-dependent adjusting travel of the adjusting piston 9 externally even after the adjusting device 7 has been assembled. -A lock nut 71 on the setscrew 69 prevents the latter from turning independently.

The adjusting device 7, of the fuel injection pump operates in the following manner.

The adjusting device 7, in its initial position during the starting of the cold internal combustion enginer has the end face 29 of the adjusting piston 9 held against the stop 41 by the return spring 35. The control rod 5 is in the fuel delivery quantity adjusting position in the full- load direction which corresponds to the cold-starting quantity, wherein its first stop 19 of the slotted hole 17 abuts against the pin 13. Thus, the position of the adjusting piston 9 of the adjusting device 7 determines the maximum quantity of fuel delivered during cold starting of the internal combustion engine, this position of the adjusting piston 9 being adjustable by the adjustable stop 41. The control rod 5 is displaced in the direction of a smaller quantity of fuel by the 11rotational-speed-dependent governor after the internal combustion engine has started, so that the stop 19 is removed from the pin 13 and the control rod 5 may be actuated independently of the adjusting device 7.

If the internal combustion engine is to be stopped. the pressure medium, preferably compressed air, is fed to the pressure chamber 31 from a reservoir (not illustrated) by way of the pressure medium passage 33. The pressure in the pressure chamber 31 increases. exceeds the force of the return spring 35 and moves the adjusting piston 9 until the end face 60 of the adjusting piston 9 abuts against the end face 59 of the sleeve 55. The radial pin 13 on the adjusting piston 9 comes into abutment against the first stop 19 in the slotted hole 17 of the control rod 5 and, during the further course of the movement of the adjusting piston 9, moves the control rod 5 in the direction of a zero delivery quantity against the force of the resilient drag member on the governor, so that the fuel feed pump feeds no more fuel to the internal combustion engine and consequently the latter is stopped. The guide ring 53 may slide freely on the adjusting piston 9 during this adjusting operation of the adjusting piston 9. when starting an internal combustion engine which is still hot, the spring element 49, which is -12lengthened by the radiated heat of the internal combustion engine, displaces the adjusting piston 9 of the adjusting device 7 towards the sleeve 55 against the force of the return spring 35 to the extent that the guide ring 53 on the adjusting piston 9 abuts against the sleeve 55. Thereby the pin 13 is displaced in the direction of a smaller delivery quantity of fuel, and the stop 19 of the control rod 5, during the adjusting movement in the direction of the starting quantity, comes into abutment against the pin 13 after a shorter travel of the control rod than that during cold starting, so that less fuel is delivered than during cold starting.

Advantageously, the spring element 49 is in the form of a so-called "memory" spring and is made from a material having a "shape memory" of the type which ensures that it always assumes the same shape at a specific temperature, irrespective of a change of shape undertaken in the meantime. This property is used here for temperature-dependent adjustment of the position of the adjusting piston in such a way that the spring acts as a strong spring when the internal combustion engine is hot, and can be deformed by the return spring 35 when the internal combustion engine is cold.

The adjusting device 7, of the fuel injection -13pump, may be mounted on a control lever on the governor or on the end of the control rod. Also, it is possible to stop the internal combustion engine pneumaticallyr and/ or to control the quantity of fuel for cold starting and to regulate the starting quantity in dependence upon temperature in acommon housing, and thus not to take up any additional installation space. The starting quantity stops being externally adjustable.

Claims

-14Claims

1. A fuel injection pump for internal combustion engines, having a housing, pump pistons disposed in line and guided in cylinder liners, each of which pistons defines a respective pump working chamber, a control rod mounted in the longitudinal direction of the pump in the pump housing and which is longitudinally displaceable by an adjusting member for the purpose of adjusting the quantity of fuel injected by the pump pistons and which is connected to the adjusting member by way of a resiliently yielding drag member, and an adjusting device having an adjusting piston which is adjustable away from a stop by a pressure medium against the force of a return spring and which acts upon the control rod by way of an intermediate member between two further stops,, which are located one behind the other in the direction of movement and are disposed on at least one part which is moved together with the control rod during the movement of the latter for adjusting the quantity of fuel injected, for limiting a travel of the control rod predetermined by the distance between the stops. wherein the adjusting piston of the adjusting device is displaceable in dependence upon the operating temperature of the internal combustion engine by a temperature-dependent spring element which is disposed -15on the periphery of the adjusting piston and which is supported against an abutment fixed relative to the housing and acts against the return spring, in such a way that the possible adjusting travel of the control rod in the direction of a full-load delivery quantity is variable by abutment of one of the further stops against the intermediate member.

2. A fuel injection pump as claimed in claim 1, wherein the temperaturedependent spring element is supported by way of a stop sleeve which is slildingly displaceable on the adjusting piston and which is brought into abutment against a stop on the adjusting piston by the spring element and brought into abutment against an adjustable stop on the housing of the adjusting device by the spring element. wherein the stop sleeve has a longitudinal slot in which is guided the intermediate member projecting radially from the adjusting piston.

3. A fuel injection pump as claimed in claim 2, wherein the end face of the adjusting piston remote from the stop sleeve and from the temperaturedependent spring element is brought by the return spring into abutment against an externally adjustable setscrew which is screwed into the end face of the housing and by which the maximum adjusting travel of the control rod in the direction of the full load -16delivery quantity is fixed during starting of the cold internal combustion engine.

4. A fuel injection pump as claimed in claim 3, wherein the temperaturedependent spring element is designed in such a way that, when the internal combustion engine is cold, is exerts no initial stressing force on the adjusting piston. or a substantially smaller initial stressing force than the return spring, and the adjusting piston is subjected to a pressure medium for the purpose of setting a zero delivery quantity position of the control rod.

5. A fuel injection pump as claimed in claim 1, wherein the pressure medium, preferably compressed air acts upon that end face of the adjusting piston which is remote from the temperature-dependent spring element.

6. A fuel injection pump as claimed in any preceding claim, wherein the return spring acting against the pressure medium or against the temperature-dependent spring element is a compression spring which is supported against a further stop fixed relative to the housing and which embraces the adjusting piston and acts upon the adjusting piston by way of a ring disposed on the periphery of the adjusting piston.

7. A fuel injection pump as claimed in any -17preceding claim, wherein the temperature-dependent spring element is a "memory" compression spring.

8. A fuel injection pump constructed and adapted to operate substantially as hereinbefore described with reference to, and as illustrated in the accompanying drawings.